Abstract

The first 50 million years of dinosaur evolution, during the Late Triassic and Early Jurassic, encompass most radiation events in the history of the group, suggesting that key macroevolutionary differentiation between clades was being established during these emergent times. In Gondwana lands, dinosaur origins is well investigated in the Late Triassic deposits of south Brazil and north-western Argentina, which include the most important global records of the oldest members of the group. Early Jurassic dinosaur-bearing sediments are, however (and especially in South America), much rarer; corresponding to an important gap in the knowledge about the evolutionary history of the group. This Project aims at developing a field program to collect dinosaur fossil remains in Late Triassic and Early Jurassic gondwanan sediments, as well as to conduct revision studies on the anatomy and systematics of various key-taxa of the group. Field work will explore deposits of Triassic age in south Brazil (Santa Maria and Caturrita formations) and Tanzania ("Tunduru beds"), and of Jurassic age in Venezuela (La Quinta Formation) and NE Brazil (Pastos Bons Formation). Already collected specimens will be the focus of indicial anatomical and phylogenetic studies, including a new stem-Averostra theropod from the Jurassic of Venezuela, as well as various basal dinosaurs from the Triassic of Rio Grande do Sul. In addition, radioisotopic (U-Pb) methods will be employed in an attempt to date the above mentioned deposits, aiming at assembling geochronologic and phylogenetic data together, in order to best understand the "tempo and mode" of the early dinosaur radiation in Gondwana. (AU)